Polyol composition and polyisocyanate-based foam prepared therefrom

ABSTRACT

A polyol composition is disclosed that comprises an aromatic polyether polyol, preferably based on the condensation product of a phenol with an aldehyde and as blowing agent, formic acid. The polyol composition finds utility in the manufacture of polyurethane and particularly polyisocyanurate foams having attractive flameretardant and reduced smoke generation characteristics.

The present invention relates to a process for preparingpolyisocyanurate foam, and also to a polyol composition, having utilityin the preparation of polyisocyanate-based foam.

Polyurethane and polyisocyanurate foam is being subjected tocontinuously changing and ever greater demands with respect to flameretardant and reduced smoke generation traits. It is also required thatsuch foams are manufactured by processes that minimizes the use ofblowing agents viewed as being harmful to the environment. Legislationhas restricted the use of many substances traditionally used as physicalblowing agent when preparing foam, and over the recent years there hasbeen an emergence of alternative physical blowing agents includinghydrocarbons, notably pentanes, and hydrofluoroalkanes such as forexample tetrafluoroethane (R-134a) and pentafluoropropane (R-245fa).

There have also been many developments in the use of chemical blowingagents such as water and carbamates. Water is an attractive agent fromthe point of view of availability and economics. However, one of itsdisadvantages is the high consumption of isocyanate and high processtemperatures associated with its use. Also in the case ofpolyisocyanurate foam, excessive amounts of water can be detrimental tofoam properties leading to for example, high foam friability. Analternative to water is formic acid, which does not bring with it thesame disadvantages. Formic acid reacts with isocyanate generating carbonmonoxide and carbon dioxide gases that function as the blowing means.

The literature contains a number of publications that disclose the useof formic acid as blowing agent when preparing polyisocyanate-basedfoams such as polyurethane or polyisocyanurate foams.

U.S. Pat. No. 4,417,002 discloses the use of formic acid in combinationwith water as blowing agent for the manufacture of polyurethane foams.

U.S. Pat. No. 5,143,945 discloses the preparation of rigidpolyurethane-polyisocyanurate foams in the presence of a blowing agentcomprising a halocarbon in combination with an organic carboxylic acid,and optionally water. The carboxylic acid can be formic acid.

U.S. Pat. No. 5,286,758 discloses the use of formic acid and formatesalts to prepare a low density rigid polyurethane under conditions ofimproved reactivity control.

U.S. Pat. No. 5,214,076 teaches the preparation of acarbodiimide-isocyanurate open celled foam from aromatic polyesterpolyols or aromatic amine polyols (ethoxylated TDA) in the presence of ablowing agent that can comprise formic acid.

U.S. Pat. Nos. 5,478,494 and 5,770,635 teach a polyol compositioncomprising a mixture of polyether polyols of differing equivalentweights and use of such composition in the presence of formic acid toprepare rigid polyurethane foams.

U.S. Pat. No. 5,762,822 teaches the manufacture of rigid polyurethanefoam from a froth foaming mixture that employs as blowing agent a C1-C4hydrofluorocarbon having a boiling point of 300K or less in combinationwith at least 2 weight percent of formic acid or salts thereof. Similarteachings are also presented in U.S. Pat. No. 5,883,146.

Despite this apparently extensive knowledge relating to formic acid asblowing agent when manufacturing polyurethane or polyisocyanurate foamthere is still a need to provide a foam that exhibits improved flameretardant performance or exhibits a reduced potential for smokegeneration when burnt. Additionally for polyisocyanurate foam, thechallenge is to combine above mentioned foam combustibilitycharacteristics with convenient processing and generally acceptable foammechanical properties.

It has now been discovered that formic acid-blown polyisocyanate-basedfoam prepared in the presence of an aromatic polyether polyol enablesthe production of foam with unexpected improvements in general physicalperformance including flame retardancy and smoke reduction.

In one aspect, this invention is a polyol composition suitable for thepreparation of a rigid polyisocyanate-based foam, containing one or morepolyether or polyester polyols and a blowing agent, wherein; (a) theblowing agent comprises formic acid; and (b) the polyol comprises anaromatic polyoxyalkylene polyol based on an initiator obtained from thecondensation of a phenol with an aldehyde.

In a second aspect, this invention is a multi component system suitablefor the preparation of a rigid polyisocyanate-based foam which comprisesas first component an aromatic polyisocyanate, and as second componentthe polyol composition as mentioned above.

In a third aspect, this invention is a process for preparing apolyisocyanate-based foam which comprises bringing together underfoam-forming conditions a polyisocyanate with the polyol composition asdescribed above.

In a fourth and fifth aspect, this invention is a polyurethane foam, ora polyisocyanurate foam, obtained by bringing together underfoam-forming conditions a polyisocyanate with a polyol compositioncharacterized in that:

-   -   a) the polyisocyanate is present in an amount to provide for an        isocyanate reaction index of from 80 to 150 (for polyurethane)        or from 150 to 600 (for polyisocyanurate); and    -   b) the polyol composition comprises (I) formic acid; and (ii) an        aromatic polyoxyalkylene polyol based on an initiator obtained        from the condensation of a phenol with an aldehyde.

In a sixth aspect, this invention is a process for preparing aclosed-celled polyisocyanurate foam by bringing into contact underfoam-forming conditions a polyisocyanate with a polyol composition inthe presence of a blowing agent mixture wherein the polyol compositioncomprises an aromatic polyester polyol and an aromatic polyether polyol;and wherein the blowing agent mixture comprises formic acid and anadditional blowing agent, which is a hydrofluoroalkane selected from thegroup consisting of tetrafluoroethane, pentafluoropropane,heptafluoropropane and pentafluorobutane, or a hydrocarbon selected fromthe group consisting of butane, pentane, cyclopentane, hexane,cyclohexane, and heptane, and the isomers thereof, and wherein thepolyisocyanate is present in an amount to provide for an isocyanatereaction index of from greater than 150 to 600.

In a seventh aspect, this invention is a laminate comprising theabove-mentioned polyurethane or polyisocyanurate foam.

The rigid polyisocyanate-based foams in accordance with this inventionare prepared by bringing together under foam-forming conditions apolyisocyanate with a particular polyol composition comprising anaromatic polyol and a blowing agent comprising formic acid. The aromaticpolyol is an aromatic polyether polyol or a combination thereof with anaromatic polyester polyol. The preferred aromatic polyether polyols arethe aromatic polyoxyalkylene polyols based on an initiator derived fromthe condensation of a phenol with an aldehyde. In a preferred embodimentof this invention, the aromatic polyoxyalkylene polyol used is oneobtained by reacting a condensate adduct of phenol and formaldehyde,with one or more alkylene oxides including ethylene oxide, propyleneoxide, and butylene oxide. Such polyols, sometimes referred to as“Novolak” initiated polyols are known to one of skill in the art, andcan be obtained by methods such as disclosed in, for example, U.S. Pat.Nos. 2,838,473; 2,938,884; 3,470,118; 3,686,101 and 4,046,721.Typically, “Novolak” starting materials are prepared by reacting aphenol (for example a cresol) with from 0.8 to 1.5 moles of formaldehydeper mole of the phenol in the presence of an acidic catalyst to form apolynuclear condensation product containing from 2.1 to 12, preferablyfrom 2.2 to 6, and more preferably from 3 to 5 phenol units/molecule.The novolak resin is then reacted with an alkylene oxide such asethylene oxide, propylene oxide, butylene oxide, or isobutylene oxide,to form an oxyalkylated product containing a plurality of hydroxylgroups. For the purpose of the present invention, preferred “Novolak”polyols are those having an average of from 3 to 6 hydroxyl moieties permolecule and an average hydroxyl equivalent weight of from 100 to 500,preferably from 100 to 300. The “Novolak” initiated polyether polyolpreferably constitutes from about 1, more preferably from about 10, morepreferably from about 20, and yet more preferably from about 25; and upto about 99, preferably to about 70, more preferably up to about 60parts by weight of the total weight of polyol composition.

The polyol composition comprises the formic acid in an amount to providefoam of the desired density. Typically the formic acid is present in anamount of from 0.5 to 8 parts per 100 parts by weight of the polyolcomposition including the formic acid. Preferably the formic acid ispresent an amount of from 1.5 parts and more preferably from 2 parts,and up to a preferred amount of 6 parts and more preferred 3.5 parts byweight. While formic acid is the carboxylic acid of preference, it isalso contemplated that minor amounts of other aliphatic mono andpolycarboxylic acids may also be employed, such as those disclosed inU.S. Pat. No. 5,143,945 column 3, lines—column 4, line 28, and includingisobutyric acid, ethylbutyric acid, and ethylhexanoic acid.

In addition to the “Novolak-” polyol and formic acid, the polyolcomposition may contain other polyether and polyester polyols along withadditional blowing agents, (for example water), catalysts, surfactants,fillers and Flame Retardant additives as commonly used in themanufacture of polyisocyanate-based foams.

Examples of additional blowing agents which can be present includehydrochlorofluorocarbons, hydrofluorocarbons and hydrocarbons, as wellas water. The additional blowing agent is preferably used in an amountof from 2 to 15 parts preferably from 4 to 10 parts, per 100 parts byweight of the polyol composition. Suitable hydrofluoroalkanes are theC₁-C₄ compounds including difluoromethane (R-32),1,1,1,2-tetrafluoroethane (R-134a), 1,1-difluoroethane (R-152a),difluorochloroethane (R-142b), trifluoromethane (R-23),heptafluoropropane (R-227a), hexafluoropropane (R136),1,1,1-trifluoroethane (R-133), fluoroethane(R-161),1,1,1,2,2-pentafluoropropane (R-245fa), pentafluoropropylene(R2125a), 1,1,1,3-tetrafluoropropane, tetrafluoropropylene (R-2134a),1,1,2,3,3-pentafluoropropane and 1,1,1,3,3-pentafluoro-n-butane. When ahydrofluorocarbon blowing agent is present, preferred istetrafluoroethane (R-134a), pentafluoropropane (R-245fa) orpentafluorobutane (R-365). Suitable hydrocarbons for use as blowingagent include nonhalogenated hydrocarbons such as butane, isobutane,2,3-dimethylbutane, n- and I-pentane isomers, hexane isomers, heptaneisomers and cycloalkanes including cyclopentane, cyclohexane andcycloheptane. Preferred hydrocarbons for use as blowing agent includecyclopentane and notably n-pentane an iso-pentane. In a preferredembodiment of this invention the polyol composition comprises a physicalblowing agent selected from the group consisting of tetrafluoroethane(R-134a), pentafluoropropane (R-245fa), pentafluorobutane (R-365),cyclopentane, n-pentane and iso-pentane. Water may also be present inthe polyol composition added intentionally as a blowing agent. Whenintending to prepare polyurethane foam advantageously water is presentin an amount of from 0.5 to 10 parts, and preferably from 1 to 6 parts,per 100 parts by weight of the polyol composition. When intending toprepare a polyisocyanurate foam, in order to obtain facilitate and givedesirable processing characteristics, it is advantageous not to exceed 2parts of water, preferably not-to exceed 1.5 parts of water, and morepreferably not to exceed 0.75 parts of water, and even to have waterabsent.

Other polyols which may be present in the polyol composition include oneor more other polyether or polyesters polyols of the kind typicallyemployed in processes to make polyurethane foam. Other compounds havingat least two isocyanate reactive hydrogen atoms may also be present, forexample polythioether polyols, polyester amides and polyacetalscontaining hydroxyl groups, aliphatic polycarbonates containing hydroxylgroups, amine terminated polyoxyalkylene polyethers, and preferably,polyester polyols, polyoxyalkylene polyether polyols, and graftdispersion polyols. Mixtures of two or more of the aforesaid materialsmay also be employed.

The term “polyester polyol” as used in this specification and claimsincludes any minor amounts of unreacted polyol remaining after thepreparation of the polyester polyol and/or unesterified polyol (forexample, glycol) added after the preparation of the polyester polyol.Suitable polyester polyols can be produced, for example, from organicdicarboxylic acids with 2 to 12 carbons, preferably aliphaticdicarboxylic acids with 4 to 6 carbons, and multivalent alcohols,preferably diols, with 2 to 12 carbons, preferably 2 to 6 carbons.Examples of dicarboxylic acids include succinic acid, glutaric acid,adipic acid, suberic acid, azelaic acid, sebacic acid,decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid,isophthalic acid, and terephthalic acid. The dicarboxylic acids can beused individually or in mixtures. Instead of the free dicarboxylicacids, the corresponding dicarboxylic acid derivatives may also be usedsuch as dicarboxylic acid mono- or di-esters of alcohols with 1 to 4carbons, or dicarboxylic acid anhydrides. Dicarboxylic acid mixtures ofsuccinic acid, glutaric acid and adipic acid in quantity ratios of20-35:35-50:20-32 parts by weight are preferred, especially adipic acid.Examples of divalent and multivalent alcohols, especially diols, includeethanediol, diethylene glycol, 1,2- and 1,3-propanediol, dipropyleneglycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,1,10-decanediol, glycerine and trimethylolpropanes, tripropylene glycol,tetraethylene glycol, tetrapropylene glycol, tetramethylene glycol,1,4-cyclohexane-dimethanol, ethanediol, diethylene glycol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, or mixtures of at leasttwo of these diols are preferred, especially mixtures of 1,4-butanediol,1,5-pentanediol, and 1,6-hexanediol. Furthermore, polyester polyols oflactones, for example, epsilon-caprolactone or hydroxycarboxylic acids,for example, omega-hydroxycaproic acid, may also be used. While thearomatic polyester polyols can be prepared from substantially purereactant materials, more complex ingredients are advantageously used,such as the side stream, waste or scrap residues from the manufacture ofphthalic acid, terephthalic acid, dimethyl terephthalate, andpolyethylene terephthalate. Other residues are dimethyl terephthalate(DMI) process residues, which are waste or scrap residues from themanufacture of DMT. The present applicants have observed that forcertain applications it is particularly advantageous for reasons of foamperformance and processing to have present in the polyol compositionboth the “Novolak” polyol and an additional aromatic polyol which can bean aromatic polyether or aromatic polyester polyol.

Polyether polyols that additionally may be present include those whichcan be obtained by known methods, For example, polyether polyols can beproduced by anionic polymerization with alkali hydroxides such as sodiumhydroxide or potassium hydroxide or alkali alcoholates, such as sodiummethylate, sodium ethylate, or potassium ethylate or potassiumisopropylate as catalysts and with the addition of at least oneinitiator molecule containing 2 to 8, preferably 3 to 8, reactivehydrogens or by cationic polymerization with Lewis acids such asantimony pentachloride, boron trifluoride etherate, etc., or bleachingearth as catalysts from one or more alkylene oxides with 2 to 4 carbonsin the alkylene radical. Any suitable alkylene oxide may be used such as1,3-propylene oxide, 1,2- and 2,3-butylene oxide, amylene oxides,styrene oxide, and preferably ethylene oxide and 1,2-propylene oxide andmixtures of these oxides. The polyalkylene polyether polyols may beprepared from other starting materials such as tetrahydrofuran andalkylene oxide-tetrahydrofuran mixtures; epihalohydrins such asepichlorohydrin; as well as aralkylene oxides such as styrene oxide. Thepolyalkylene polyether polyols may have either primary or secondaryhydroxyl groups, preferably secondary hydroxyl groups from the additionof propylene oxide onto an initiator because these groups are slower toreact. Included among the polyether polyols are polyoxyethylene glycol,polyoxypropylene glycol, polyoxybutylene glycol, polytetramethyleneglycol, block copolymers, for example, combinations of polyoxypropyleneand polyoxyethylene glycols, poly-1,2-oxybutylene and polyoxyethyleneglycols, poly-1,4-tetramethylene and polyoxyethylene glycols, andcopolymer glycols prepared from blends or sequential addition of two ormore alkylene oxides. The polyalkylene polyether polyols may be preparedby any known process such as, 5 for example, the process disclosed byWurtz in 1859 and Encyclopedia of Chemical Technology, Vol. 7, pp.257-262, published by Interscience Publishers, Inc. (1951) or in U.S.Pat. No. 1,922,459. Polyethers which are preferred include the alkyleneoxide addition products of polyhydric alcohols such as ethylene glycol,propylene glycol, dipropylene glycol, trimethylene glycol, 1,2-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol,hydroquinone, resorcinol glycerol, glycerine, 1,1,1-trimethylol-propane,1,1,1-trimethylolethane, pentaerythritol, 1,2,6-hexanetriol, a-methylglucoside, sucrose, and sorbitol. Also included within the term“polyhydric alcohol” are compounds derived from phenol such as2,2-bis(4-hydroxyphenyl)-propane, commonly known as Bisphenol A.Particularly preferred in the polyol composition is at least one polyolwhich is initiated with a compound having at least two primary orsecondary amine groups, a polyhydric alcohol having 4 or more hydroxylgroups, such as sucrose, or a mixture of initiators employing apolyhydric alcohol having at least 4 hydroxyl groups and compoundshaving at least two primary or secondary amine groups. Suitable organicamine initiators which may be condensed with alkylene oxides includearomatic amines-such as aniline, N-alkylphenylene-diamines, 2,4′-,2,2′-, and 4,4′-methylenedianiline, 2,6- or 2,4-toluenediamine, vicinaltoluenediamines, o-chloro-aniline, p-aminoaniline,1,5-diaminonaphthalene, methylene dianiline, the various condensationproducts of aniline and formaldehyde, and the isomeric diaminotoluenes;and aliphatic amines such as mono-, di-, and trialkanolamines, ethylenediamine, propylene diamine, diethylenetriamine, methylamine,triisopropanolamine, 1,3-diaminopropane, 1,3-diaminobutane, and1,4-diaminobutane. Preferable amines include monoethanolamine, vicinaltoluenediamines, ethylenediamines, and propylenediamine. Yet anotherclass of aromatic polyether polyols contemplated for use in thisinvention are the Mannich-based polyol an alkylene oxide adduct ofphenol/formaldehyde/alkanolamine resin, frequently called a “Mannich”polyol such as disclosed in U.S. Pat. Nos. 4,883,826; 4,939,182; and5,120,815.

When the blowing agent composition includes physical blowing agents suchas, for example, HFC245fa, HFC134a, HFC365mfc or HFC227, or hydrocarbonssuch as for example n-pentane, the combination of an aromatic polyesterpolyol and an aromatic polyether polyols is particularly preferred inorder to achieve desirable flame retardant and smoke suppressantcharacteristics together with attractive storage stability of the polyolcomposition and convenient foam processing.

In the practice of the present invention, the applicants have-observedthat for the purpose of enhancing foam integrity and improving surfaceadhesion it is advantageous to incorporated small amounts of highequivalent weight polyether polyols such as are typically used in moldedflexible polyurethanes, for example, VORANOL 1421 available from The DowChemical Company and understood to be a glycerine-initiatedpolyoxypropylene-oxyethylene polyol having a molecular weight ofapproximately 5100 and an oxyethylene content of approximately 70percent.

In addition to the foregoing components, it is often desirable to havecertain other ingredients present in the polyol composition for thepurpose of facilitating the subsequent use in preparing cellularpolymers. Among these additional ingredients are catalysts, surfactants,preservatives, colorants, antioxidants, flame retardants, reinforcingagents, stabilizers and fillers. In making polyurethane foam, it isgenerally highly preferred to employ a minor amount of a surfactant tostabilize the foaming reaction mixture until it cures. Such surfactantsadvantageously comprise a liquid or solid organosilicone surfactant.Other, less preferred surfactants include polyethylene glycol ethers oflong-chain alcohols, tertiary amine or alkaolamine salts of long-chainallyl acid sulfate esters, alkyl sulfonic esters and alkyl arylsulfonicacids. Such surfactants are employed in amounts sufficient to stabilizethe foaming reaction mixture against collapse and the formation oflarge, uneven cells. Typically, 0.2 to 3 parts of the surfactant per 100parts by weight polyol composition are sufficient for this purpose.

Such flame retardants advantageously present include for exampleexfoliating graphite, phosphonate esters, phosphate esters, halogenatedphosphate esters or a combination thereof Phosphonate esters for use inthe present invention can be represented by the formula R—P(O)(OR′)(OR″)where R, R and R″ are each independently an alkyl having 1 to 4 carbonatoms. Preferred members of this group are dimethyl methylphosphonate(DMMP) and diethyl ethyl phosphonate (DEEP). Phosphate esters which canbe used in the present invention are trialkyl phosphates, such astriethyl phosphate, and tricresyl phosphate. When used, the phosphonateor phosphate ester flame retardants are present in the final foam at alevel of from 0.5 to 20 percent by weight of the final foam. Preferablythey are 1 to 15 percent by weight of the final foam. More preferablythey constitute 2 to 10 percent by weight of the final foam. Halogenatedphosphate esters which are associated with fire retardation are known inthe art and can be represented by the general formulaP(O)(OR′X′n)(OR″X″n)(OR′″X′″n), where R′, R″ and R′″ are eachindependently an alkyl having 1 to 4 carbon atoms, X′, X″ and X′″ areeach independently a halogen and n is an integer from 1 to 3. Examplesof halogenated phosphate esters include 2-chloroethanol phosphate;1-chloro-2-propanol phosphate [tris(1-chloro-2-propyl) phosphate](TCPP); 1,3-dichloro-2-propanol phosphate also calledtris(1,3-dichloro-2-propyl) phosphate; tri(2-chloroethyl) phosphate; tri(2,2- dichloroisopropyl) phosphate; tri (2,3-dibromopropyl) phosphate;tri (11,3-dichloropropyl)phosphate; tetrakis(2-chloroethyl) ethylenediphosphate; bis(2-chloroethyl) 2-chloroethylphosphonate; cliphosphates[2-chloroethyl diphosphate]; tetrakis (2-chloroethyl)ethylenediphosphate; tris-(2-chloroethyl)-phosphate,tris-(2-chloropropyl)phosphate, tris-(2,3-dibromopropyl)-phosphate,tris(1,3-dichloropropyl)phosphate tetrakis (2-chloroethyl- ethylenediphosphate and tetrakis(2-chloroethyl) ethyleneoxyethylenediphosphate.Tribromonopentyl chloroalkyl phosphates as disclosed in EP 0 735 039having the formula [(BrCH₂)₃C—CH₂O]_(n)PO (OCYHCH₂Cl)₃-where Yrepresents a hydrogen, an alkyl having 1 to 3 carbon atoms, orchloroalkyl group and n is from 0. 95 to 1.15 may also be used.

One or more catalysts for the reaction of the polyol (and water, ifpresent) with the polyisocyanate are advantageously used. Any suitableurethane catalyst may be used, including tertiary amine compounds andorganometallic compounds. Exemplary tertiary amine compounds includetriethylenediamine, N-methylmorpholine, N,N-dimethylcyclohexylamine,pentamethyldiethylenetriamine, tetramethylethylenediamine,1-methyl-4-dimethylaminoethylpiperazine,3-methoxy-N-dimethylpropylamine, N-ethylmorpholine, diethylethanolamine,N-cocomorpholine, N,N-dimethyl- N′,N′-dimethylisopropylpropylenediamine, N,N-diethyl-3-diethylaminopropylamine anddimethylbenzylamine. Exemplary organometallic catalysts includeorganomercury, organolead, organoferric and organotin catalysts, withorganotin catalysts being preferred among these. Suitable tin catalystsinclude stannous chloride, tin salts of carboxylic acids such asdibutyltin di-laurate, as well as other organometallic compounds such asare disclosed in U.S. Pat. No. 2,846,408. A catalyst for thetrimerization of polyisocyanates, resulting in a polyisocyanurate, suchas an alkali metal alkoxide may also optionally be employed herein. Suchcatalysts are used in an amount which measurably increases the rate ofpolyurethane or polyisocyanurate formation. Typical amounts are 0.001 to3 parts of catalyst per 100 parts by weight of total polyol.

A polyisocyanate-based foam is obtained by bringing together the abovedescribed polyol composition under foaming forming conditions with apolyisocyanate. In this manner polyurethane or polyisocyanurate foam canbe prepared. Polyisocyanates useful in making the foam include aliphaticand cycloaliphatic and preferably aromatic polyisocyanates orcombinations thereof, advantageously having an average of from 2 to 3.5,preferably from 2.4 to 3.2, and more preferably from 2.8 to 3.2isocyanate groups per molecule. A crude polyisocyanate may also be usedin the practice of this invention, such as crude toluene diisocyanateobtained by the phosgenation of a mixture of toluene diamine or thecrude diphenylmethane diisocyanate obtained by the phosgenation of crudemethylene diphenylamine. The preferred polyisocyanates are aromaticpolyisocyanates such as disclosed in U.S. Pat. No. 3,215,652. Especiallypreferred are methylene-bridged polyphenyl polyisocyanates and mixturesthereof with crude diphenylmethane diisocyanate, due to their ability tocross-link the polyurethane.

For the preparation of a polyurethane foam the polyisocyanate is presentin an amount, relative to the polyol composition, so as to provide anisocyanate reaction index of from 80 to 150, preferably from 90 to 130.An isocyanate index of 100 corresponds to one isocyanate equivalent peractive hydrogen atom present in the polyol composition. For thepreparation of a polyisocyanurate foam the polyisocyanate is present inan amount to provide an isocyanate reaction index of from 150 to 600,preferably from 200 to 500. The polyol composition of this invention isparticularly useful in the preparation of polyisocyanurate foam.

In general, the rigid foams may be produced by discontinuous orcontinuous processes, including the process referred to generally as thediscontinuous panel process (DCP) and continuous lamination, with thefoaming reaction and subsequent curing being carried out in molds or onconveyors. When utilizing the foams in laminates, the facing may beflexible, for example, aluminum foil or coated paper, or may be a rigidmaterial such as plaster-board, polyester facing or steel facing. Otherprocesses to prepare construction foams are known as spray and blockfoams.

The rigid foam of the present invention are for the most partclosed-cell foam. By closed-cells it is meant that at least 75 percent,preferably 80 percent or greater, and more preferably 85 percent or moreof the cells are closed. In a preferred embodiment, 90 percent or moreof the cells are closed. Because of the closed-cell structures, therigid polyurethanes of the present invention are useful for thermalinsulation applications such as roofing, sheathing and in-situ sprayapplications.

The following examples are given to illustrate the invention and shouldnot be interpreted as limiting it in any way. Unless stated otherwise,all parts and percentages are by weight. The following abbreviationsidentify various materials used in the Examples.

-   -   Polyol A: A “Novolak” polyol being a oxypropylene-oxyalkylene        adduct based on a phenol-formaldehyde condensate having an        average functionality of about 3.3. Polyol hydroxyl number is        196.    -   Polyol B A polyester polyol, TEROL 198 available from Oxid        understood to have a hydroxyl number 198.    -   Polyol C A glycerine-initiated oxypropylene-oxyethylene polyol,        VORANOL 1421, available from The Dow Chemical Company. Hydroxyl        Number 35.

Polyol D A sucrose initiated oxypropylene-oxyethylene polyol, VORANOL280, available from The Dow Chemical Company. Hydroxyl Number 280 DEEPDiethyl ethylphosphonate TCPP Trichloroisopropylphosphate MEG ethyleneglycol DABCO DC5598 Surfactant, available from Air Products DABCO TMRCatalyst, available from Air Products DABCO K15 Catalyst, available fromAir Products PMDETA pentamethyldiethylenetriamine DMCHAdimethylcyclohexylamine Toyocat DM70 Catalyst, available from TosohCurithane 206 Catalyst available from The Dow Chemical Company FormicAcid Purity 98 percent, supplied by Incofar n-pentane commercial gradeas provided by Synthesis ISO A VORANATE 600, A higher functionality (2.9to 3) crude diphenylmethane diisocyanate available from The Dow ChemicalCompany ISO B VORANATE 220, A standard grade crude diphenylmethanediisocyanate available from The Dow Chemical Company

FOAM EXAMPLES 1-9

Foams 1 to 9 (2, 4, 7 and 9 are comparative Foams) are prepared using aCannon A40 high pressure machine. Reactants and amounts are indicated inthe following table. Foams 1-4 have been evaluated in the production ofmetal-faced continuous laminate panels. Foams 5 to 9 have been evaluatedin the production of discontinuous panels. Foams prepared in thepresence of formic acid exhibit a notably stronger flame retardant andsmoke suppressant characteristics than those foams prepared in theabsence of the acid. Foams prepared in the presence of formic acid andpentane, provided both surprisingly good flame retardant and reducedsmoke generation traits; such performance in the presence of pentane hadnot been expected giving consideration to the normal flammableproperties of pentane.

Comparative example Foam 9 show that use of a polyol compositioncomprising uniquely an aromatic polyester polyol is unattractive withobservation of poor skin curing, resulting in more difficult processing.

A further observation is that this invention provides for polyolcompositions of attractive storage stability where such compositionsincludes as blowing agent, HFC245fa (Foam 8).

FOAM EXAMPLE 10

A polyisocyanurate foam is prepared in a manner similar to Foams 1-9with reactants as noted below. In this instance the polyol compositionis a combination of an aromatic polyester polyol and an aromaticpolyether polyol with good blend stability in the presence of theblowing agent, pentafluoropropane (245fa). 47 pbw TERATE 4026, apolyester polyol from Kosa, 7 OH value 205 Polyol C 10 TERACOL 5902, aTDA initiated, oxypropylene oxyethylene polyol available from The DowChemical Company, OH value 375 5 DEEP 9 TCPP 6 TEP surfactant 1.6Surfactant 0.3 DMCHA 2.2 CURITHANE 206 0.3 water 2.6 formic acid 9.1 Hfc245fa Iso A (Index) 170 pbw/(300) Reactivity (CT/GT) 4/44 Free risedensity (kg/m3) 38.3

The foam is observed to have a Butler chimney flame spread of 15.5 cm; aweight retention of 93.4 percent; and a smoke development (NBS) of 59.Processing characteristics of the foam are attractive with a 100 percentskin cure being noted in about 7 minutes at a mold temperature of 45C.TABLE 1 Pbw Foam 1 Foam 2* Foam 3 Foam 4* Foam 5 Foam 6 Foam 7* Foam 8Foam 9* Polyol A 30.1 30 31 31 52.3 45.4 51 24.8 Polyol B 25 25 30.530.5 / / / 24.7 47.6 (*) Polyol C 11.5 11.5 / / / / / Polyol D / / 9.19.1 / / / DEEP 11.5 11.4 9.8 9.8 8 12.9 11 8 12.89 TCPP 14 14 9.8 9.8 3031.7 31.9 30 30.25 MEG / / 0.5 0.5 / / / L6900 / / / / / 1.98 1.5 DABCODC5598 1.8 1.8 2.95 2.95 3 / / 3 3 DMCHA 0.47 0.4 0.2 / / 0.05 DMEE / // / / 0.2 / Toyocat DM70 0.2 PMDETA / 0.07 0.1 0.1 / / / CURITHANE 52 // 4.92 4.92 / 3.03 / Dabco K15 0.33 CURITHANE 206 1.74 2.2 / / 1.5 / 0.71.45 1.5 DABCO TMR / / 1.0 1.0 / / / Water 1.91 3.15 / 1.2 / 1.98 3.121.98 Formic Acid 1.45 / 1.6 / 4.99 2.78 / 4 2.78 HFC 245fa / / / / / / /4 / n-Pentane / / 9 9 / / / / / ISO A (Index) 188.5 231 180 180 / /(300) (300) (340) (320) ISO B / / / / 160 168 180 143 179 (293) (240)(247) (290) (240) Polyol blend stability Clear, Clear, / Clear, Clear,Clear, Clear, stable stable stable stable stable stable Reactivity CT/GT(secs) 5/42 5/26 6/41 6/95 12/100 13/88 6/83 20/105 Free-Rise Coredensity 44.9 43.3 38.9 34 31 35 32.4 35 (kg/m³) DIN 4102 B2 rating (cm)5 / 6.5 9.2 6 9 12.5 6.4 7.8 Butler Chimney test Flame spread 15.9 cm 20cm / Weight retention 92.6 91.5 89.8 87 percent Smoke development (NBS)137 176 66 86 % skin cure >70 25 100 25 100 100 70 percent 100 50percent (45-50 C. mold temp) percent percent percent percent percentpercent (soft percent (soft at 7 min at 7 min at 5 min at 5 min 12 min12 min foam) 12′ 12 min foam) 12′(*) Terate 2540, polyester polyol from Kosa, hydroxyl number 250

EXAMPLES 11-15 Effect of Formic Acid on Flammability Characteristics ofPolyisocyanurate Foams

Foams 11 to 15 are prepared under hand mix conditions in accordance withthe reactants and amounts indicated in the Table 2. The combustioncharacteristics of the foams as monitored by cone calorimetry indicatethat use of formic acid in a select range provides a robust performancedespite a variance in isocyanate reaction. TABLE 2 Foam Foam Foam FoamFoam Pbw 11 12 13 14 15 TERATE 4026 45 45 45 45 45 Polyol C 7 7 7 7 7TERACOL 5902 10 10 10 10 10 EMPILAN NP 9 2 2 2 2 2 DEEP 5 5 5 5 5 TCPP 99 9 9 9 TEP 6 6 6 6 6 DABCO DC5598 1.5 1.5 1.5 1.5 1.5 Water 0.2 0.2 0.20.2 0.2 DMCHA 0.3 0.3 0.3 0.3 0.3 CURITHANE 52 1.8 2.1 1.2 3 1.2 FormicAcid 3 2.1 1.2 3 1.2 HFC 245fa 8 11 14.5 7 17 ISO A to give ReactionIndex 300 287 380 294 385 of: Theoretical trimer percent 43.4 41.5 49.943.3 50.4 Reactivity CT/GT/TFT (secs) 8 8 9 8 8 @ 20° C. 75 55 70 60 58145 124 150 135 110 Free-Rise Core density (kg/m³) 36.3 35.5 37.6 35.835.6 Cone Calorimeter Peak Heat 96 102 84.5 77.5 113 Release (kW/m2)Cone Calorimeter mass loss % 39.5 40.5 41.5 41 43

FOAM EXAMPLES 16-19 Flammability Characteristics of Formic Acid ModifiedPolyisocyanurate Foams with Various Physical Blowing Agents

Foams 16 to 19, typical of a discontinuous panel system, are preparedusing a Cannon A40 high pressure machine. Reactants and amounts areindicated in Table 3.

The results indicate the ability to use formic acid in combination withother blowing agents when preparing polyisocyanurate foams that exhibitgood flame retardant characteristics.

All foaming systems were observed as having easy processingcharacteristics good attractive physical properties including adhesionto metal facers. Use of the formic acid as sole blowing agent whilestill providing for good FR properties is observed to give foams withpoorer physical properties than these reported here. It is alsodesirable to utilize water in restricted amounts within the system; useof significantly elevated amounts of water leads to foam systems thatare more arduous to process and foams that may be friable and inferiorin their FR performance TABLE 3 Foam Foam Foam Foam Pbw 16 17 18 19TERATE 4026 45 45 45 45 Polyol C 7 7 7 7 TERACOL 5902 10 10 10 10SURFACTANT 2 2 2 2 DEEP 5 5 5 5 TCPP 9 9 9 9 TEP 6 6 6 6 DABCO DC55981.5 1.5 1.5 1.5 Water 0.2 0.3 0.2 0.2 DMCHA 0.3 0.3 0.3 0.3 CURITHANE 522.2 2.2 2.2 2.2 Formic Acid 2.6 2.6 2.6 2.6 HCFC 141B 12 HFC 245fa 12n-Pentane 6 HFC365/227 (93;7 wt ratio) 12 ISO A to give Reaction Index310 310 310 290 of: Reactivity CT/GT/(secs) @ 634 432 541 438 20° C.Free-Rise Core density (kg/m³) 35.5 35.3 40.3 35.4 Cone Calorimeter PeakHeat 94 88.5 99 103 Release (kW/m2) Cone Calorimeter mass loss 39.5 43.041.0 40.0 after 500 s (percent) LOI (ASTM 2863) 29.5 28.5 29 / DIN 4102B2 (cm) 5.2 5.7 5.5 6

Other embodiments of the invention will be apparent to those skilled inthe art from a consideration of this specification or practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only with the true scope and spiritof the invention being indicated by the following claims.

1) A polyol composition suitable for the preparation of a rigidpolyisocyanate-based foam containing one or more polyether or polyesterpolyols and a blowing agent, wherein; a) the blowing agent comprisesformic acid; and b) the polyol comprises an aromatic polyoxyalkylenepolyol based on an initiator obtained from the condensation of a phenolwith an aldehyde. 2) The polyol composition of claim 1 whichadditionally comprises a physical blowing agent. 3) The polyolcomposition of claim 2 wherein the physical blowing agent is ahydrocarbon selected from the group consisting of butane, pentane,cyclopentane, hexane, cyclohexane, and heptane, and the isomers thereof.4) The polyol composition of claim 2 wherein the physical blowing agentis a C₁-C₄ hydrofluoroalkane or hydrochlorofluoroalkane. 5) The polyolcomposition of claim 4 wherein the physical blowing agent is ahydrofluoroalkane selected from the group consisting of difluoromethane,difluoroethane, tetrafluoroethane, pentafluoropropane andhexafluorobutane. 6) The polyol composition of claim 1 where in thearomatic polyoxyalkylene polyol based on an initiator obtained from thecondensation of phenol with formaldehyde. 7) The polyol composition ofclaim 6 wherein the aromatic polyoxyalkylene polyol is present in anamount of at least 20 weight percent based on total weight of the polyolcomposition. 8) The polyol composition of claim 7 that further comprisesan aromatic polyester polyol. 9) A multi component system suitable forthe preparation of rigid polyisocyanate-based foam that comprises asfirst component an aromatic polyisocyanate, and as second component apolyol composition as claimed in claim
 1. 10) A process for preparing apolyisocyanate-based foam which comprises bringing together underfoam-forming conditions a polyisocyanate with a polyol composition asclaimed in claim
 1. 11) The process of claim 10 where in thepolyisocyanate is present in an amount to provide for an isocyanatereaction index of from 80 to
 150. 12) The process of claim 10 where inthe polyisocyanate is present in an amount to provide for an isocyanatereaction index of from 150 to
 600. 13) A polyurethane foam obtained bybringing together under foam-forming conditions a polyisocyanate with apolyol composition characterized in that: a) the polyisocyanate ispresent in an mount to provide for an isocyanate reaction index of from80 to 150; and b) the polyol composition comprises (I) formic acid; and(ii) an aromatic polyoxyalkylene polyol based on an initiator obtainedfrom the condensation of a phenol with an aldehyde. 14) Apolyisocyanurate foam obtained by bringing together under foam-formingconditions a polyisocyanate with a polyol composition characterized inthat: a) the polyisocyanate is present in an mount to provide for anisocyanate reaction index of from 150 to 600; and b) the polyolcomposition comprises (1) formic acid; and (ii) an aromaticpolyoxyalkylene polyol based on an initiator obtained from thecondensation of a phenol with an aldehyde. 15) A laminate comprising thefoam of claim 13 or claim
 14. 16) A process for preparing aclosed-celled polyisocyanurate foam by bringing into contact underfoam-forming conditions a polyisocyanate with a polyol composition inthe presence of a blowing agent mixture wherein the polyol compositioncomprises an aromatic polyester polyol and an aromatic polyether polyol;and wherein the blowing agent mixture comprises formic acid and ahydrofluoroalkane selected from the group consisting oftetrafluoroethane, pentafluoropropane, heptafluoropropane andpentafluorobutane, and characterized in that the polyisocyanate ispresent in an amount to provide for an isocyanate reaction index of fromgreater than 150 to
 600. 17) The process of claim 16 wherein water ispresent in an amount of from 0 to 2 parts by weight per 100 parts of thecombined weight of the polyol composition and blowing agent mixture. 18)The process of claim 16 wherein the aromatic polyether polyol comprisesa toluenediamine-initiated polyol, a Mannich base-initiated polyol, amethylene diphenylamine-initiated polyol, a phenol-acetonecondensate-initiated polyol or a phenol-formaldehydecondensate-initiated polyol. 19) A process for preparing a closed-celledpolyisocyanurate foam by bringing into contact under foam-formingconditions a polyisocyanate with a polyol composition in the presence ofa blowing agent mixture wherein the polyol composition comprises anaromatic polyester polyol and an aromatic polyether polyol; and whereinthe blowing agent mixture comprises formic acid and a hydrocarbonselected from the group consisting of butane, pentane, cyclopentane,hexane, cyclohexane, and heptane, and the isomers thereof andcharacterized in that the polyisocyanate is present in an amount toprovide for an isocyanate reaction index of from greater than 150 to600. 20) The process of claim 16 or 19, wherein the polyisocyanate is anaromatic polyisocyanate having on average from 2.8 to 3.2 isocyanategroups per molecule. 21) A two component foam forming system thatcomprises: a) an aromatic polyisocyanates having an average of from 2.8to 3.2 isocyanate groups per molecule; and b) a polyol composition thatcontains (i) an aromatic polyester polyol and an aromatic polyetherpolyol; and (ii) a blowing agent mixture which comprises formic acid anda hydrofluoroalkane selected from the group consisting oftetrafluoroethane, pentafluoropropane, heptafluoropropane andpentafluorobutane. 22) A two component foam forming system thatcomprises: a) an aromatic polyisocyanates having an average of from 2.8to 3.2 isocyanate groups per molecule; and b) a polyol composition thatcontains: (i) an aromatic polyester polyol and an aromatic polyetherpolyol; and (ii) a blowing agent mixture which comprises formic acid anda hydrocarbon selected from the group consisting of butane, pentane,cyclopentane, hexane, cyclohexane, and heptane, and the isomers thereof